Patent Application DE-A-41,19,514 describes a unit for supplying packets of cigarettes, which comprises a first and second belt conveyor located one over the other and respectively defining a first and second path having a common portion, and two diverging portions downstream from the common portion; and a routing device located at the common portion and having a suction chamber with a suction port along the first belt conveyor to suck the packets on to the belt of the first conveyor and feed the packets along the first path. When the suction chamber is idle, the packets are conveyed by the second conveyor, on which the packets rest by force of gravity.
Though highly versatile in dividing the main stream of packets of cigarettes as required, the above unit has drawbacks when dividing the main stream into two secondary streams, each with a spacing equal to twice that of the main stream, i.e. when the packets of cigarettes in the main stream are fed alternately along the first and second path, which would call for rapidly alternating on-off operation of the suction chamber. Rapidly alternating vacuums are difficult to achieve, on account of the inevitable inertia involved, and also produce rapid wear of control members, such as valves and respective actuating members.